The present invention relates to an oven for heating items such as foods with gas energy, and has particular utility in the cook-chill-rethermalization process. The oven preferably uses the relatively high heat release of natural gas which is burned outside the insulated oven walls, providing uniform high velocity forced air convection heating and high production capacities.
Prior approaches to rethermalization ovens have used heating elements, often electrical in nature, which are placed inside the oven cavity and arranged in geometries that attempt to evenly distribute the heat input to the oven cavity and the food therein. These ovens are characterized by long heating times, wide variations in food temperatures and relatively small capacities. For example, U.S. Pat. No. 4,722,683 (Royer) shows a rethermalization oven whose preferred embodiment employs an electrical heating coil situated in an interior heating chamber, although Royer also suggests the alternative use of a gas flame within the same chamber. U.S. Pat. No. 4,671,250 (Hurley) also provides an interior gas burner which is directly in front of and spaced but a short distance from the interior circulating blower. Similarly, U.S. Pat. No. 4,648,377 (Van Camp) shows a gas flame inside the insulated oven walls for providing hot air to a circulating blower through internal heat exchange tubes that partially block the flow of air from the blower.
In contrast to this prior art wherein combustion occurs inside the oven, the present invention introduces heated air (including combustion products) into the oven from an exterior gas burner via a conduit or "fire tube" in a manner such that the air flow from a recirculating blower within the oven is not blocked nor is its return air flow impeded. Thus, air flow velocities to and from both sides of the oven are nearly identical and provide uniform temperatures within the oven cavity for the food or other items being heated.